This invention relates to a developing apparatus and image forming apparatus built in, for example, a copier, a printer and the like employing electrophotography.
A developing apparatus of this type comprises a developing roller. A layer thickness regulation blade abuts on the developing roller in a plane or an edge portion of a free end of a layer thickness regulation blade linearly abuts on the developing roller to provide electric charge to a toner and regulate a thickness of a toner layer to a constant extent.
In the above-mentioned developing apparatus, an inelastic or elastic layer thickness regulation blade abuts on an elastic or inelastic developing roller to regulate the thickness of the toner layer.
In a conventional developing apparatus, however, there are problems as explained below.
In a case where the layer thickness regulation blade abuts on the developing roller in a plane, the thickness of the toner layer formed on the developing roller is greatly varied in accordance with a distance from an abutment portion (i.e. a nip portion) to the free end of the layer thickness regulation blade.
That is, a toner retention portion is generated at a part from the nip portion to the free end of the layer thickness regulation blade. For this reason, the toner of the toner retention portion may be excessively pushed between the developing roller and the layer thickness regulation blade by a conveying force of the developing roller and the toner may spill over.
The spillage of toner can be prevented by enhancing the pressurizing force of the layer thickness regulation blade to the developing roller.
In this case, however, much frictional heat is generated at the nip portion and toner fixation occurs at the layer thickness regulation blade. Further, as an agglomerate such as toner, dust and the like is retained at the toner retention portion, stripes and the like are generated on the toner layer on the developing roller by the fixing toner and the agglomerate and, image quality is thereby deteriorated.
On the other hand, in the developing apparatus where the free end of the layer thickness regulation blade abuts on the developing roller, as it is difficult to adjust an abutting force of the layer thickness regulation blade on the developing roller and it is very difficult to uniformly maintain the nip along the longitudinal direction of the developing roller, a uniform toner layer cannot be formed stably and a preferable output image cannot be obtained.
This invention is accomplished in consideration of the above circumstances, and the object of this invention is to provide a developing apparatus and image forming apparatus capable of stably forming a developer layer having a predetermined thickness on a developing device, preventing a developer from spilling over from a layer thickness regulation device, and preventing stripes from being generated on the developer layer by developer fixation or foreign matters.
A developing apparatus of this invention comprises a developing device composed of an inelastic body, for feeding a developer to a portion to be developed and developing the portion, and a layer thickness regulation device composed of an inelastic body, for abutting on the developing device and regulating a thickness of the developer fed to the developed portion to a certain extent. This developing apparatus has the following relation:
R1 sin(Cosxe2x88x921((R1xe2x88x92r1)/R1)) less than X1 less than R1 sin(Cosxe2x88x921((R1xe2x88x923r1)/R1))
where a volume average grain size of the developer is represented by r1, a radius of the developing device is represented by R1, and a distance from an abutment portion of the layer thickness regulation device and the developing device to a free end of the layer thickness regulation device is represented by X1.
A developing apparatus of this invention comprises a developing device for feeding a developer to a portion to be developed and developing the portion, and a layer thickness regulation device for abutting on the developing device and regulating a thickness of the developer fed to the developed portion to a certain extent. One of the developing device and the layer thickness regulation device is composed of an inelastic body and the other is composed of an elastic body, and this developing apparatus has the following relation:
R1 sin(Cosxe2x88x921((R1xe2x88x92r1)/R1)) less than X2xe2x88x92Z/2 less than R1 sin(Cosxe2x88x921((R1xe2x88x923r1)/R1))
where a volume average grain size of the developer is represented by r1, a radius of the developing device is represented by R1, a width of an abutment portion of the layer thickness regulation device and the developing device is represented by Z, and a distance from a center of the abutment portion to a free end of the layer thickness regulation device is represented by X2.
An image forming apparatus of this invention comprises an image carrier for carrying an electrostatic latent image, a developing device composed of an inelastic body, for feeding a developer to the electrostatic latent image on the image carrier and developing the electrostatic latent image, a layer thickness regulation device composed of an inelastic body, for abutting on the developing device and regulating a thickness of the developer fed to the electrostatic latent image to a certain extent, and a transfer device for transferring a developer image developed on the image carrier to a member to be transferred. This image forming apparatus has the following relation:
R1 sin(Cosxe2x88x921((R1xe2x88x92r1)/R1)) less than X1 less than R1 sin(Cosxe2x88x921((R1xe2x88x923r1)/R1))
where a volume average grain size of the developer is represented by r1, a radius of the developing device is represented by R1, and a distance from an abutment portion of the layer thickness regulation device and the developing device to a free end of the layer thickness regulation device is represented by X1.
An image forming apparatus of this invention comprises an image carrier for carrying an electrostatic latent image, a developing device for feeding a developer to the electrostatic latent image on the image carrier and developing the electrostatic latent image, a layer thickness regulation device for abutting on the developing device and regulating a thickness of the developer fed to the electrostatic latent image to a certain extent, and a transfer device for transferring a developer image developed on the image carrier to a member to be transferred. One of the developing device and the layer thickness regulation device is composed of an inelastic body and the other is composed of an elastic body, and this developing apparatus has the following relation:
R1 sin(Cosxe2x88x921((R1xe2x88x92r1)/R1)) less than X2xe2x88x92Z/2 less than R1 sin(Cosxe2x88x921((R1xe2x88x923r1)/R1))
where a volume average grain size of the developer is represented by r1, a radius of the developing device is represented by R1, a width of an abutment portion of the layer thickness regulation device and the developing device is represented by Z, and a distance from a center of the abutment portion to a free end of the layer thickness regulation device is represented by X2.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.